Photo album: Fathers and fighters

Inside the Octagon, ferocious UFC and WEC fighters go by a bevy of menacing nicknames: The Crowbar, Batman, Lil' Heathen... but outside, many of them go by just three even more powerful letters: "Dad."

Inside the Octagon, ferocious UFC and WEC fighters go by a bevy of menacing nicknames: The Crowbar, Batman, Lil' Heathen... but outside, many of them go by just three even more powerful letters: "Dad." Click to see photo album

Take Vladimir Matyushenko, aka The Janitor, who's headlining the UFC's first-ever fight card in San Diego on August 1. Just 21 years old when his son was born, he raised the boy himself -- all of their extended family still lives in Belarus. Today, Roman Matyushenko is a great martial artist with a promising MMA career ahead of him who just graded from Air Force boot camp.

“Being a father is the hardest and greatest challenge I have ever faced; but it is also the most fun, significant, and fulfilling experience of my life," he says. My son, Roman, has brought the best out of me, and I am grateful to him for that. ”

To celebrate Father's Day, we created this album of pictures of fighters with their own fathers and with their children.